Toner for developing electrostatic images, image forming method and image forming apparatus

Claim 2

A toner for developing electrostatic images, comprising: a binder resin and a colorant, wherein the binder resin comprises a vinyl copolymer having an acid anhydride group, and the binder resin has a total acid value (A) of 2 - 100 mgKOH/g and a total acid value (B) attributable to acid anhydride group of below 6 mgKOH/g so that [(B)/(A)] x 100 is 60 % or less.

Claim 3

The toner according to Claim 1, wherein the binder resin has a total acid value (A) of 5 - 70 mgKOH/g.

Claim 4

The toner according to Claim 1, wherein the binder resin has a total acid value (A) of 5 - 50 mgKOH/g.

Claim 5

The toner according to Claim 1, wherein the binder resin has a total acid value (B) attributable to acid anhydride group of 0.1 mgKOH/g or above and below 6 mgKOH/g.

Claim 6

The toner according to Claim 1, wherein the binder resin has a total acid value (B) attributable to acid anhydride group of 0.5 - 5.5 mgKOH/g.

Claim 7

The toner according to Claim 1, wherein the value [(B)/(A)] x 100 of the binder resin is 2 - 50 %.

Claim 8

The toner according to Claim 1, wherein the value [(B)/(A)] x 100 of the binder resin is 3 - 40 %.

Claim 9

The toner according to Claim 1, wherein the binder resin has a total acid value (A) of 5 - 70 mgKOH/g, a total acid value (B) of 0.1 mgKOH/g or above and below 6 mgKOH/g, and a value [(B)/(A)] x 100 of 2 -50 %.

Claim 10

The toner according to Claim 1, wherein the binder resin has a total acid value (A) of 5 - 50 mgKOH/g, a total acid value (B) of 0.5 - 5.5 kgKOH/g, and a value [(B)/(A)] x 100 of 3 - 40 %.

Claim 11

The toner according to Claim 1, wherein the vinyl copolymer has a dibasic acid group, a dibasic acid monoester group and a dibasic acid anhydride group.

Claim 12

The toner according to Claim 1, wherein the vinyl copolymer comprises a styrene copolymer having a dicarboxylic acid anhydride group, a dicarboxylic acid group and a dicarboxylic acid monoester group.

Claim 13

The toner according to Claim 1, wherein the vinyl copolymer has at least a styrene unit, a maleic acid unit, a maleic acid anhydride unit and a maleic acid monoester unit.

Claim 14

The toner according to Claim 1, wherein the vinyl copolymer has at least a styrene unit, an acrylate ester unit, a maleic acid unit, a maleic acid anhydride unit and a maleic acid monoester unit.

Claim 15

The toner according to Claim 1, wherein the vinyl copolymer has at least a styrene unit, a methacrylate unit, a maleic acid unit, a maleic acid anhydride unit and a maleic acid monoester unit.

Claim 16

The toner according to Claim 1, wherein the vinyl copolymer has been prepared by subjecting a monomer composition comprising at least a styrene monomer and an unsaturated dicarboxylic acid monoester to solution polymerization to form a styrene copolymer, dissolving the styrene copolymer in a monomer composition comprising at least a styrene monomer to form a polymerizable composition, and subjecting the polymerizable composition to suspension polymerization.

Claim 17

The toner according to Claim 1, wherein the colorant comprises a magnetic material.

Claim 18

The toner according to Claim 16, wherein the magnetic material has a number-average particle size of 0.1 - 2 microns, and a coercive force (Hc) of 20 - 150 oersted, a saturation magnetization (as) of 50 - 200 emu/g and a remanence (a,) of 2 - 20 emu/g under application of 10 kilo-oersted.

Claim 19

The toner according to Claim 17, wherein the magnetic material has a number-average particle size of 0.1 - 0.5 micron.

Claim 20

The toner according to Claim 16, which comprises a magnetic toner having a volume-average particle size of 4 - 10 microns.

Claim 21

The toner according to Claim 19, wherein the magnetic toner has a volume-average particle size of 4 - 9 microns.

Claim 22

The toner according to Claim 19, wherein the magnetic toner contains 20 - 200 wt. parts of the magnetic material per 100 wt. parts of the resin.

Claim 23

The toner according to Claim 19, wherein the magnetic toner contains 40 - 150 wt. parts of the magnetic material per 100 wt. parts of the resin.

Claim 24

The toner according to Claim 19, wherein the magnetic toner comprises 12 % by number or more of magnetic toner particles having a particle size of 5 microns or smaller, 33 % by number or less of magnetic toner particles having a particle size of 8 - 12.7 microns, and 2 % by volume or less of magnetic toner particles having a particle size of 16 microns or larger.

Claim 25

The toner according to Claim 19, wherein the magnetic toner contains 12 - 60 % by number of magnetic toner particles of 5 microns or smaller, and satisfies the condition of N/V = -0.04N + k, wherein N is a number of 12 - 60 denoting the content in terms of % by number of the toner particles of 5 microns or smaller, V is a number denoting the content in terms of % by volume of the toner particles of 5 microns or smaller, and k is a number of 4.5 - 6.5.

Claim 26

An image forming method, comprising: disposing a latent image-bearing member for holding an electrostatic image thereon and a toner-carrying member for carrying a magnetic toner with a prescribed gap at a developing station; the magnetic toner comprising a binder resin and magnetic powder and having a volume-average particle size of 4 - 10 microns, wherein the binder resin comprises a vinyl copolymer having an acid anhydride group, and the binder resin has a total acid value (A) of 2 - 100 mgKOH/g and a total acid value (B) attributable to acid anhydride group of below 6 mgKOH/g so that [(B)/(A)] x 100 is 60 % or less; conveying the magnetic toner in a layer carried on the toner-carrying member and regulated in a thickness thinner than the prescribed gap to the developing station; and applying an alternating bias voltage comprising a DC bias voltage and an unsymmetrical AC bias voltage in superposition between the toner-carrying member and the latent image-bearing member at the developing station to provide an alternating bias electric field comprising a development-side voltage component and a reverse-development side voltage component, the development-side voltage component having a magnitude equal to or larger than that of the reverse development-side voltage component and a duration smaller than that of the reverse-development side voltage component, so that the magnetic toner on the toner-carrying member is transferred to the latent image-bearing member to develop the electrostatic image thereon at the developing station.

Claim 27

An image forming method, comprising: disposing a latent image-bearing member for holding an electrostatic image thereon and a toner-carrying member for carrying a magnetic toner with a prescribed gap at a developing station; the magnetic toner comprising a binder resin and magnetic powder and having a volume-average particle size of 4 - 10 microns, wherein the binder resin comprises a vinyl copolymer having an acid anhydride group, and the binder resin has a total acid value (A) of 2 - 100 mgKOH/g and a total acid value (B) attributable to acid anhydride group of below 6 mgKOH/g so that [(B)/(A)] x 100 is 60 % or less; conveying the magnetic toner in a layer carried on the toner-carrying member and regulated in a thickness thinner than the prescribed gap to the developing station; and applying an alternating bias voltage comprising a DC bias voltage and an unsymmetrical AC bias voltage in superposition between the toner-carrying member and the latent image-bearing member at the developing station to provide an alternating bias electric field comprising a development-side voltage component and a reverse-development side voltage component, the development-side voltage component having a magnitude equal to or larger than that of the reverse development-side voltage component and a duration smaller than that of the reverse-development side voltage component, so that the magnetic toner on the toner-carrying member is transferred to the latent image-bearing member to develop the electrostatic image thereon at the developing station.

Claim 28

The image forming method according to Claim 25, wherein the alternating bias voltage has a frequency of 1.0 - 5.0 KHz.

Claim 29

The image forming method according to Claim 25, wherein the alternating bias voltage has a duty factor of 10 - 40 %.

Claim 30

The image forming method according to Claim 25, wherein the alternating bias voltage has a peak-to-peak value of 1.0 - 2.0 KV.

Claim 31

The image forming method according to Claim 25, wherein said alternating bias voltage has a frequency of 1.0 - 5.0 KHz, a peak-to-peak voltage of 1.0 - 2.0 KV and a duty factor of 10 - 40 %, and the magnetic toner contains 12 - 60 % by number of toner particles of 5 microns or smaller.

Claim 32

The image forming method according to Claim 25, wherein the latent image-bearing member comprises a photosensitive layer of a-Si.

Claim 33

The image forming method according to Claim 25, wherein said magnetic toner comprises a toner according to any one of Claims 2 to 24.

Claim 34

An image forming apparatus, comprising: a latent image-bearing member for holding an electrostatic image thereon, a toner-carrying member for carrying a layer of a magnetic toner thereon, a toner vessel for holding the magnetic toner to be supplied to the toner-carrying member, a toner layer-regulating member for regulating the magnetic toner layer on the toner-carrying member, and a bias application means for applying an alternating bias voltage comprising a DC bias voltage and an unsymmetrical AC bias voltage in superposition between the toner-carrying member and the latent image-bearing member, wherein the latent image-bearing member and the toner-carrying member are disposed with a prescribed gap therebetween at a developing station; the toner layer-regulating means is disposed to regulate the magnetic toner layer on the toner-carrying member in a thickness thinner than the prescribed gap; the magnetic toner comprises a binder resin and magnetic powder and has a volume-average particle size of 4 - 10 microns, the binder resin comprises a vinyl copolymer having an acid anhydride group, and the binder resin has a total acid value (A) of 2 - 100 mgKOH/g and a total acid value (B) attributable to acid anhydride group of below 6 mgKOH/g so that [(B)/(A)] x 100 is 60 % or less; and the bias application means is disposed to provide an alternating bias electric field comprising a development-side voltage component and a reverse-development side voltage component, the development-side voltage component having a magnitude equal to or larger than that of the reverse development-side voltage component and a duration smaller than that of the reverse-development side voltage component, so that the magnetic toner on the toner-carrying member is transferred to the latent image-bearing member to develop the electrostatic image thereon at the developing station.

Claim 35

An image forming apparatus, comprising: a latent image-bearing member for holding an electrostatic image thereon, a toner-carrying member for carrying a layer of a magnetic toner thereon, a toner vessel for holding the magnetic toner to be supplied to the toner-carrying member, a toner layer-regulating member for regulating the magnetic toner layer on the toner-carrying member, and a bias application means for applying an alternating bias voltage comprising a DC bias voltage and an unsymmetrical AC bias voltage in superposition between the toner-carrying member and the latent image-bearing member, wherein the latent image-bearing member and the toner-carrying member are disposed with a prescribed gap therebetween at a developing station; the toner layer-regulating means is disposed to regulate the magnetic toner layer on the toner-carrying member in a thickness thinner than the prescribed gap; the magnetic toner comprises a binder resin and magnetic powder and has a volume-average particle size of 4 - 10 microns, the binder resin comprises a vinyl copolymer having an acid anhydride group, and the binder resin has a total acid value (A) of 2 - 100 mgKOH/g and a total acid value (B) attributable to acid anhydride group of below 6 mgKOH/g so that [(B)/(A)] x 100 is 60 % or less; and the bias application means is disposed to provide an alternating bias electric field comprising a development-side voltage component and a reverse-development side voltage component, the development-side voltage component having a magnitude equal to or larger than that of the reverse development-side voltage component and a duration smaller than that of the reverse-development side voltage component, so that the magnetic toner on the toner-carrying member is transferred to the latent image-bearing member to develop the electrostatic image thereon at the developing station.

Claim 36

The image forming apparatus according to Claim 32, wherein the bias application means applies an alternating bias voltage having a frequency of 1.0 -5.0 KHz.

Claim 37

The image forming apparatus according to Claim 32, wherein the bias application means provides an alternating bias voltage having a duty factor of 10 -40 %.

Claim 38

The image forming apparatus according to Claim 32, wherein the alternating bias voltage has a peak-to-peak value of 1.0 - 2.0 KV.

Claim 39

The image forming apparatus according to Claim 32, wherein said alternating bias voltage has a frequency of 1.0 - 5.0 KHz, a peak-to-peak voltage of 1.0 - 2.0 KV and a duty factor of 10 - 40 %, and the magnetic toner contains 12 - 60 % by number of toner particles of 5 microns or smaller.

Claim 40

The image forming apparatus according to Claim 32, wherein the latent image-bearing member comprises a photosensitive layer of a-Si.

Claim 41

The image forming apparatus according to Claim 32, wherein said magnetic toner comprises a toner according to any one of Claims 2 to 24.